Computer Simulation on Terahertz Emission from Intrinsic Josephson Junctions of High-T_c Superconductors

Solving coupled nonlinear sine-Gordon equations and Maxwell equations numerically, we study the electromagnetic and superconducting properties of the single crystal of high-$T_c$ superconductor $\rm{Bi_2Sr_2CaCu_2O_{8+\delta}}$ with a static magnetic field applied parallel to the $ab$-plane and a dc current fed in along the c-axis. Cavity resonances of transverse plasma occur in the intrinsic Josephson junctions with frequencies in terahertz regime. It is revealed that the electromagnetic wave can transmit from the junctions into space. The emitted energy counted by the Poynting vector is about $400\rm{W/cm^2}$. The frequency as well as the energy of emission can be tuned almost continuously by the current and magnetic field.